Killing Two Birds with One Stone
by Sakura1221
Summary: The Gleeful Twins should learn to take proper precautions before summoning a demon. But hey, It's not like it matters anyways since one of them will be a vessel to the most powerful dream-demon. Isn't that what they wanted? Power? Bill Cipher is at their service. [Reverse Falls AU Cipher x Pines]


Anywho, a small something for the Reverse Falls AU (although looking back on it, it would've been so much more cooler if I had Pine Dipper instead of Gleeful Dipper, but oh well.) Because school got in the way of my fanfics, i'm three weeks late on updating **Deep Waters **and I have a slight writers block I'm hoping to get rid of by writing this... _thing_. The whole thing is told in Dipper's pov (although third person)

And, some headcanons of mine involving blood, yup. So maybe demonic possession, body horror, Mabel's being more emotional than before and Bill (I'm not going with whiny blue lil Bill here, sorry) is enjoying all of this too much.

**Disclaimer: I do not own Gravity Falls or any of the characters mentioned below (sadly :cc ), it's rightful owner is Alex Hirsch, the preview picture does not belong to me either, it belongs to Aktheneroth on DeviantArt. I only own the writing.**

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><p><strong>Killing Two Birds With One Stone<strong>

They've been over the plan countless times before, not like they weren't sure or prepared for it. He could speak the language of the dead and languages that made his human ears bleed, Mabel could conjure up spells out of thin air like the back of her hand and do it without as much as flick or her wrist or the slight movement of her lips. They could float and cast spells, they could set things on fire and get away with it, they've gone into people's mind and played with people's lives as if they were simple puppets in a puppeteer show, but then again, that's all it was to them.

A simple show.

So summoning a dream-demon was a thing that seemed ridiculous, they could do it right away, without precautions and certainly without worries. But he's against it, he's confident on his powers, he assures his sister who simply rolls her eyes in that typical way that she does when she's annoyed, and he tells her that maybe just taking some precautions wouldn't hurt at all.

She says it hurts her ego, he rolls his eyes and remains quiet. They share a simple glance before she's going over the list of items they have.

They have the black candles lined up in each side, forming a triangle. They have the runes made on a thin and precise line that circles around said triangle, they have the name of the demon they want to summon written on blood, _their_ blood, on a special piece of paper from one of the many binding books they have. They also have the dead body of a man who couldn't be ten years older than them in the middle, and they barely cast a glance at his deformed form.

Mabel snaps by the time she's done pacing around, clearly impatient and she's got this look on her eye that screams just how excited she is, not because the demon might be cute, she corrects him with a huff, but because she's going to be binding a really powerful demon. He corrects her and tells her that _they're_ going to be binding a dream-demon.

Then she retorts by saying that he hadn't been the one getting his hands dirty getting a vessel, or finding the binding spells. But he's memorized them and he's pretty sure that she has no knowledge of how to say it correctly, so she shuts up and demands him to move it along.

They have a show in a couple of hours and some extra help wouldn't be bad, so he agrees and runs his hands through his hair and begins to chant a wordy and complicated spell that leave his mouth and tingles the back of his tongue, leaves a sour and awful sticky feeling at the back of his throat and is bound to damage his vocal chords. His eyes glow blue and he's very much aware of the fact that his body is engulfed in the same glow, that his feet are no longer on the ground and that every black candle are lit up in blue flames that lick at his skin and grow.

Then, just as soon as it happened, he feels a twist on his stomach, powerful and his lips do not scream in a human language, he shouts out in a strange language that make the room shake and doesn't stop until he's down on the ground, gripping his stomach and sweaty and all the while Mabel hasn't even batted an eyelash at him. She's looking at the vessel as if expecting something.

And the minutes go by.

more and more.

She frowns.

"Is that it?" She asks with slight disappointment but by now it's overpowered by the raging shout that she gives out afterward, _"Is that it!?"_

And Dipper really wants to speak, despite the awful feeling his stomach is going through, and he stands up and opens his mouth and he cringes slightly when guttural sounds that made no sense to Mabel but to him, reach his ears. Mabel is beyond annoyed, and then she's storming up towards him, and doesn't bother to hide the unamused look on her face, not even as she stands in front of him, grabs his chin and tilts it upwards before demanding for him to speak.

Dipper shakes his head and Mabel digs her sharp nail on his skin, drawing out the tiniest bit of blood and he hisses.

"_C'mon._"

"W̢̕͟e̴͞ ̢d̵̀͝id͜͡ ͘͞i͘͢͞t̨̀ ͝ŕ͡i̛ght͜͏̛." and even though he knows she cannot understand what he said, she's already took notice of the way the room was sucked out of its colour only to be given it again, the sound of bones popping back together to how they belong and the shock that ran through both their bodies. And she turns around, moves out of the way to let him see and the sight before him makes him furious, satisfied but at the same time speechless. For starters, he really wanted his voice back, this was not part of the plan. He could already tell that his vocal chords had snapped, just like the vessel's body emitted right now.

He hated not being in control. So, _so_ much.

So with whatever ounce of energy he has, he stands up straight, goes to stand besides his twin sister and watches as the vessel moves in ungodly ways, how his head tilts back in an unnatural way and the room is quiet except for the sound of bones relocating and he can't help but ask just what happened to their vessel that seemed to be so... deformed.

And Mabel gives him a simple shrug, not paying much attention to his question, and answers that the guy was too much of a pest and that she had him run over by a truck multiple times, and he nods. Because that's so like her, and it's also so like her how after the body stops moving and writhing, and it stands up almost, groggily and bothered and confused and radiates this powerful aura, she goes up to him, steps down his chest, _hard, _with her heels and smiles sweetly.

"Bill Cipher, dream-demon. The name's Mabel Gleeful, sweetheart." And she keeps talking and talking in that sweet way that make his stomach rot inside out and he can feel the twitch of his lips as they want to break out into a satisfying smirk. They have just binded a really powerful demon.

He should feel happy, or proud. But then again, they're better, powerful, and this was a piece of cake.

Then he feels four eyes on him, and he blinks, a blank look on his face and he skims over Mabel's body, how the vessel seems to not mind the weight but his eye (and oh, Mabel failed to mention that their vessel was missing an organ, delightful) showed just how in shock he was, still, he could see the rage, the shame that the demon held.

"So, I'm assuming you're a fan of constellations or?" The dream-demon asks, tilting his head in a way no human should tilt their head lest they be on the ground. And Dipper doesn't say anything, simply looks down at the demon like he holds some power over him, and of course he does, and he sneers.

Dipper was well aware the demon was making fun of his birthmark, but he wears it uncovered and doesn't mind it, not when it glows the cyan colour that Cipher's eyes have, or the same colour of Mabel's and his attires. Certainly not when it glows just like vision, when he opens his mouth, and all he sees is blue and blue and more blue and this sickening feeling on his stomach is also blue and it's disgusting and burns his throat.

And he vomits.

It's thick and black and extremely heavy and burns his skin but he can't feel it very much, he's barely aware of the feeling. He knows it's hot, he knows the texture, even though he has never encountered such thing before. And his blue eyes, they move towards Cipher's body and he realizes just what exactly the black goop is, it's the same liquid that runs down the man's arms and seems to consist of it, and he shoots a knowing look at Mabel who does the same. And the silence of the room is broken by Cipher's obnoxious laugh.

And he keeps laughing, and laughing and Mabel becomes extremely irritated, because she presses down harder than she has on the body that Cipher's now possessing, and hisses to tell him to stop laughing. Last thing they needed was their Great-Uncle coming into the room, and Dipper agrees. Because while Stan was often submissive over their choices, he'd try to put a foot down, especially when he was vomiting black goop and they had a man with unnatural proportions being stepped down by a fifteen-year old girl in the middle of a binding circle.

So he watches it, cleans his mouth and tries to forget about the bitter taste of the goop (he can still taste it, it's awful) and watches as Mabel digs her heel so far into the body that it's probably pierced skin, and then Cipher makes a hurt noise, like the wind was knocked out of his lungs. Before his smile widens and he's laughing like a lunatic over the blood.

Dipper wasn't sure what he expected to ooze out of the deep wound the dream-demon held, a part of him begged for it to be some weird demon-goo. Not the dark familiar red liquid that pooled on Cipher's clothing oh so beautifully. So he excuses himself, closes the door behind him and screams his voice raw in a language that makes the back of his throat hurt and itch and damn, he shouldn't be this excited.

He retreats to his bedroom with nothing more than dirty clothes, probably stained forever, sweaty and still feeling awful. He takes everything off and turns the lights off with a snap of his fingers, The glow of his eyes leave approximately an hour later, and his throat still hurts. And somehow, all along the mix, his wrist had started to itch.

So then when he can finally breathe again, straight, correct, without feeling like his stomach was doing flips. And his eyes stopped glowing and the bitter taste still hadn't left, he traces the new burning mark on his wrist, a simple providence eye that glows blue in the dark and he smiles to himself. Having a dream-demon might not be so bad after all.

So he hopes, that this wasn't a big mistake, (he's Dipper Gleeful, he knows what he's doing. He's gone over this plan countless times, he knows he hasn't messed up. _He can't )_ and that the excitement of seeing the blood on Cipher's body is not gonna make him smile every day of his life, because he in his life has never felt so aroused.

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><p>He wakes up earlier than usual, the room is still dark and his body hurts all over, it feels heavy, too heavy. But then again, it is too early and his eyes are glowing bright blue and his sister is screaming and smashing things downstairs and he doesn't really feel like dealing with Mabel's tantrums at- He glances at the clock besides his bed.<p>

4:00am

Mabel's done this before, sometimes she would barge into his room asking where he had put her jewelry, the magic ones, and he would say he had no idea where they were at, and he didn't lie. Dipper had his own type of magic, he didn't need Mabel's jewelry, after all, what use would he get from them? Nothing. So he turns and turns on his bed until he can no longer hear Mabel's screaming or her smashing things, she's just being Mabel. She's just being that, the girl who got influenced rather easily by her emotions.

Except that when he goes downstair to have breakfast and finds Mabel unusually calm after screaming and smashing, everything's a mess and she's in the middle of this mess which mostly consists of broken shards and broken jewelry and auras and whispers and screams come out of each and every single broken thing, and her thighs are covered in deep cuts that bleed out black goop that seems to flow out and flow out, does he realize that this is not Mabel just being Mabel.

This is something else, and quite frankly he's not even worried about her.

He's furious. Just what's happening here? This isn't supposed to happen, and Cipher was nowhere to be seen.

He walks around the broken shards, ignores the threats that are whispered out of the pendants and jewelry, places a hand on Mabel's form and asks her if she's okay. Then just like that the whole room spins and his head meets the cold floor. The wind is knocked out of him and he coughs, effectively getting some of the black goop on Mabel's cheek.

And extra set of eyes.

Okay.

"Ugh, you still haven't stopped talking gibberish." She groans, sits down on his belly and holds his arms above his head. Dipper blinks.

" Y̵͡o̴͟ų ̡͞ha̴v̕e͢ a͘n̵͞o͢t̸̛ḩe̸͡ŗ̷̀ ̛͞p͟a̧̡i̴͡r ͏o͞f͞ ̵e̴ý̛e͏s̸͠ ̧͞si̸̢s̨͝ţ̵͡er͞.̶̕͘ "

Mabel blinks, her lips recoil in disgust before she's wiping off the black goop out of her face, "and your eyes are still blue. You're not using magic, dear."

" I̢͠'ve not҉i͏̴ce͡d "

Dipper's very aware of the fact that she can't understand him, but not being able to speak, it rubs him off in a wrong way. He's not the chatty one of the duo, Mabel's good at it, she has a way with words which come into her advantage at most, if not, all the time. She's influenced so much more easily by her emotions, if she weren't his sister he would actually recoil in disgust at the sight of her being so friendly with others below their level.

So he speaks, and tells her that she's acting childishly, that she's wasting her time freaking out over a pair of eyes and that she can easily get rid of them. He says it calmly, the language is no longer something that bothers him, but the scratching is still ever so present on his throat. Because this was he does, he comforts her and spoils her, even if Mabel doesn't always want it. But he does it anyways.

It might've been the way he was speaking, so calmly, or the way Mabel had loosened up her grip and he took one arm out to extend, and stroke her cheek in that way that they've both done so before, but her eyes, her cyan eyes had darkened so much that he would've thought it was just his imagination, but he knows this look and in the small amount that he had before she had raised her fist above her head and brought it down to his face in a blur, he could've reached for his amulet, casted a barrel and gotten her off of him with a simple touch.

But he doesn't and she manages to break his nose.

And even that doesn't stop her, she goes to hit him again, and again, and again. And she doesn't stop until Dipper's face is swollen and there's blood on her knuckles and Dipper's eyes still haven't stopped glowing and he groans, at the sight of his blood on his sister's hand. It takes Mabel a minute, before she's staring down at him with tears streaming down her face and her lip swollen from the biting.

"I _despise you so much_, brother-dearest." And she gets up, helps him stand up, brushes her disheveled hair with her bloody hand and sighs.

The room is quiet except for the whispers that come out of the amulets and somehow, even after all of this, he's not disturbed. Hurt? yes. His face hurts like hell, but he doesn't say anything about it. He can feel his skin reducing from the swelling, stops hurting, and all because of the blue-glowing hand of his that's covered in a white gloved, now stained black, that fixes him up.

And he gives Mabel a small smile.

" B͝e̴̛t͠t̛́͘e̵̵̛r͏͘?͡ " He asks, and Mabel glares, but nods.

So she might've understood that.

They spend the rest of the morning having breakfast, Stan comes out around midday from his bedroom and doesn't even ask about the mess that's the living room. Or the fact that Dipper's vomiting black goop every now and then and he's also speaking a language that is not even close to english. And Mabel's holding a perfectly normal conversation as she paints her nail, and Stan ignores even more so how his great-niece has another set of eyes just below her regular ones.

So he goes and tells them to get ready for tonight's show, and they both simply give the man a stare and a small confident smile.

But internally, Dipper's sure that they're both losing it. And he feels sick to the core, but because he's for once no in charge of everything that's happening to them. Just before the show, he vomits and vomits on top of Mabel when she's working on a spell to get rid of their current predicament, which earns him a slap from his twin and more curses at whatever it is that's causing all of this.

He vomits again once before going out in the stage and while performing the feeling of the hot sticky substance is forgotten when they both start to do their tricks. And maybe it's because he's the master of the show (and Mabel of course) and he's in control of everything's thats going to happen, he knows how the crowd will react upon the most simplest tricks. Loves how they 'oow' and 'aww' at the way they both walk in and present themselves as 'The Psychic Twins" (even though Mabel was the one to speak). He's the puppeteer and he can control everyone with a flick of his wrist.

And in the middle of the crowd, he spots him, Cipher's casually there, floating, and he's got this smirk upon his face and Dipper shoots Mabel a look and he's sure that she already knows he's there, and they don't need to speak. The show ends and just like that, they're back to not being in control. And he punches a wall and takes deep breaths before meeting his sister backstage.

Her amulet is glowing bright, before it flickers into nothing and he can feel his eyes go back to their glowing nature, and Mabel's extra set of eyes are back in place. He gives her a nod and the female calls Cipher, who's at her side right away and he takes notice of the way her left wrist, glows, and he realizes that he hadn't seen that before. So he had the right wrist and she the left.

He excuses himself, tells Mabel (and she blinks as if he wasn't talking to her, _rude._) that he'll be back shortly and he goes to his bathroom and vomits,_ again_.

Except this time it leaves him dizzy and he tries to shoo it away.

He walks the halls of the mansion, finds Mabel and Cipher in the living room in a compromising position, and he simply shuts the door behind him. They don't even bat an eyelash, Bill's too preoccupied with the teen who sits on his lap and purrs sweet nothings and laughs at his little jokes, and his hand is treading dangerously low on Mabel's back.

But Dipper doesn't say anything, this is Mabel and when she's like this, it's because she gets whatever it is she wants through flattery.

"C'mon Cipher," Mabel hisses out, playing with a lock of the man's hair. "We know you're the one behind it."

Bill's face turns into that of fake comfort, both twins can see it right away. Dipper more so than Mabel, she's done that face so many times before.

"Why, I feel offended! First you bind me without my consent and now you're accusing me of possessing your bodies?"

And something clicks on Dipper's head just like that, and Mabel seems to be studying Cipher's facial expression before turning around to face Dipper.

"What do you mean, possessing our bodies?"

"You two messed up the binding spell." He says it like it's the most obvious thing in the world, and to Dipper Gleeful is not the most obvious thing in the world. He went over it, he thinks, no, he's _sure _they did everything right. However, the obvious thing right now is that Mabel's standing up and marching towards him and she seems like she's about to hit him but she doesn't.

Instead she takes it upon herself in rage to insult him, to tell him that he's responsible for all of this. That they're turning into monsters because of his careless mistake, and he fights back, although more calmly but still, a bit agitated, that he's sure they did everything right, because they did and Bill's just speaking nonsense to freak them out.

Or so he wished.

"Oh, Pine Tree, how I wish I was speaking lies." Both twins looked up at the dream-demon, and Dipper noticed the familiar smell of rotting and decaying. "But I'm not, your sister can _see_ it."

And then he starts to laugh and Mabel has this murderous look on her face.

_"Haha! Get it? 'See it' because she has four eyes!"_

The Gleeful twins wait until the demon's done laughing, both of them clearly annoyed by the demon's foolish behaviour. Or more so Mabel, Dipper was going over their summoning spells and bindings, before clicking his tongue.

" Ý͝ơ̵̷ư̸͞'̵r͠e̢͡ ̸w̕ro̴̶͘n͜͟g҉̧,̀͡ ̕w҉̀͢e ̵͡͡d́i̧d͞ ̸͢ȩv͘er̸̕͠y̡t̷̵͞h̴̨ín̸ģ ͞͝r͜͏i̸̧͟gh̸t̨. "

"Ah yes, you're right and wrong." Bill stated, before circling around both Gleefuls. "See, you're at fault here. You didn't use the strongest binding spell there was, kiddo." The way he said it made Dipper open his mouth before closing it.

Yeah but-

"And that baffles me because, you overestimated my power." Bill gave out an obnoxious laugh.

Mabel on the other hand, was a walking machine fueled by hate and rage, all of which was going to be directed at Dipper himself, until Bill spoke again.

"And Shooting Star here, didn't get a competent vessel for me to acquire."

The room fell dead silent after that. Dipper knew they should've gone over the whole thing countless times, but this was their zone! They breathed magic! They could easily tame Cipher's butt right now, and he could do nothing about it! Yeah! So he tells Bill this exact same thing, only to have the demon laugh at him in his own face and Dipper lets out a low annoyed sound.

"So what kiddo? _For how long_?" Bill grinned from ear to ear, "With the way you're both are, I'd say it won't be long before I posses another body."

"..."

"I wonder, who it'll be though!" Bill mused to himself, "wouldn't want it to be Pine Tree over here, you got a strange liking towards blood, kid."

Dipper frowned, clearly uncomfortable but didn't break eye contact with the demon. He was boiling inside, hot, blinding rage, over everything. Over Bill, over his sister, over every damned book on spells and demons, and especially over himself.

"Why us?" Mabel finally asked, tapping her foot impatiently.

"Because, I need a stronger vessel. And I just so happen to have _two_ at my disposition right now."

Dipper glared, " Who͟ ҉s̴à͜y̶͘͝ş̴͟ ͠w͟͟ę͠'̛͢d̸ ̧̛g̢̛͡iv̧è ̨̀o͟͟͞ưr̴̕͠ ̸b͝od̷͢͏i̸̴͝e͜͢҉s̶̸ ̵̶t̴͢o̡҉ ̛̀ý͜ó̕u̴̕?̴͝͏ "

"You don't have much of a choice kiddo. With the way the two of you have been absorbing my powers, and let me tell you, you two need a lot of control, and the way this body is rotting because, like I said, your sister here was not capable of getting a more competent vessel. There's no other option, not like I'm complaining, after all, I wasn't the idiot who binded a demon without a vessel that's fit for it."

And he knows Bill's right, but still, it infuriated him. He could feel the substance coming up his throat, hot, _so hot._

"But hey! Look at the bright side! You're getting the powers you wanted, isn't that what the two of you wanted?" Bill grins.

And they both remain quiet.

And Dipper couldn't think of another moment, that topped this one in the recklessness that is their life.

He finally asks Bill if there's anything they can do about it, and the demon gives them both this creepy smile that manages to send shivers down their spines. He says a deal, in which they bring him a new vessel each month in exchange for him to teach them how to wield his powers and not take over their bodies.

And they don't have much of a choice, it's either their lifes or other's. So they accept the deal, and as the blue flames that lick away at their hands as they shake hands with the demon, Dipper only manages one coherent thought.

He hopes they're doing the right thing, because they're no longer the puppeteers.

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><p><strong>Please review uwu Critiques are always welcome and appreciated. <strong>

**Also, if there are any grammatical mistakes, please don't be afraid to tell me.**


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